A synchronous machine operating in accordance with transverse flux principles consists of an armature winding in the form of a circular coil co-axial with a rotor. The armature winding links the flux generated by permanent magnets mounted on the rim of the rotor by means of a series of stator cores. An advantage of this topology is that the section of the stator cores can be increased so that more flux can be carried without encroaching on the space required by the armature winding.
In previous designs of transverse flux machines the rotor rims carry two side by side rows of permanent magnets separated by an insulating spacer. Two circular stator coils are used and stator cores are incorporated on both the inside and the outside of the rotor so that useful torque is provided at both the inner and outer surfaces of the rotor.
Problems with machines of this design are that they are difficult to assemble as the stator coils are enclosed within the stator cores. The rotor rims are long and lack stiffness and the rotor is subject to deflections as it has little stiffness against radial shock. The radial force on the stator cores as the flux alternates causes radial movement of the stator casing. This zero order stator case vibration is difficult to alleviate without adding thickness to the casing.